Doug Schoepf knew the statistical trend portended trouble ahead. As the number of foals born in Minnesota declined steeply in recent years, the director of racing at Canterbury Park understood it would become more and more difficult to fill races for Minnesota-bred horses at the Shakopee track.

Still, Schoepf didn’t expect only three horses to enter the Victor S. Myers Stakes on July 4, forcing it to be canceled. That made him a little nervous about Saturday’s Minnesota Derby, the track’s other major stakes race for 3-year-old Minnesota-bred colts and geldings.

“I was very surprised [about the Myers],’’ Schoepf said. “That’s the first time that’s ever happened. It just shows how depleted the numbers are.’’

Two late nominations boosted the Derby field to eight, still not a robust number. The population of 2-year-old horses is smaller yet, with enough to fill only six races so far this season — fewer than half the number held only three years ago. The numbers crunch promises to be worse next year, after the foal crop of 2012 tumbled to an all-time low of 96.

There is hope on the horizon. Last summer’s 10-year, $75 million purse-enhancement agreement between Canterbury and the Shakopee Mdewakanton Sioux Community gave an immediate jolt to the breeding industry, with 259 thoroughbred foals born in the state this year. The purse increase also has boosted the market for Minnesota-bred horses, with a big jump in the number being offered at Saturday’s annual horse auction held by the Minnesota Thoroughbred Association.

In the short term, though, Schoepf is prepared for the task of making do with very few.

“The numbers have really dropped off, and next year, they’ll drop off even more,’’ he said. “In previous years, you could count on every two weeks, you were going to get a Minnesota-bred 2-year-old [males] race and 2-year-old fillies race to go. That hasn’t happened this year.

“We hope we’ll be able to fill those races next year. But we may be running very short, five-horse fields for 2-year-olds and some 3-year-old races. It’s going to be a challenge, no doubt about it.’’

Minnesota Racing Commission statistics show the number of thoroughbred foals born in the state has declined every year since 344 were delivered in 2005. Shrinking purses at Canterbury Park, and uncertainty about the track’s future, caused breeders to cut back or leave the business.

In 2010, 182 foals were produced in Minnesota, and Schoepf said 100 are registered to race at Canterbury as 3-year-olds this summer. The foal number dropped to 131 in 2011, with 60 registered to race. Even among the horses registered, some will be injured or will not be ready to run, further reducing the pool.

Through the first week in August 2010, Schoepf was able to put together 15 races for 2-year-old thoroughbreds, with an average of 7.6 horses in each. In the same time period last year, he could muster only eight races, with an average field size of 7.25. This year’s six races have drawn only 6.83 starters.

Schoepf said he is carding more races for older Minnesota-bred horses, and he expects to continue relying on them in the short term — particularly with fewer than 100 horses eligible to begin their racing careers as 2-year-olds next year.

“A lot of the babies don’t even make it to the races, so a number that’s already low gets depleted quite a bit more,’’ he said. “The older horses have helped keep Minnesota-bred racing going. I hope we can keep them racing until we get the numbers up for the younger ones.’’

This year’s foal numbers indicate rising fortunes for Minnesota’s racing industry, and the MTA’s horse sale also is on an upward trend. Of the 96 foals born last year, more than half will be offered for sale at Saturday’s auction, an annual event held at Canterbury. MTA executive director Kay King said 71 horses have been consigned to this year’s sale, up sharply from the 44 entered last year.

The purse-enhancement agreement sent prices soaring at last year’s sale, and King expects another increase this year. She said sale catalogs usually are sent to potential buyers in nearby states, but she has gotten requests this year from people as far away as Texas, Florida and New York. More new owners also are getting into the game, particularly in partnerships.

“There are 51 Minnesota-bred yearlings in the sale, because people realize there’s a market for them again,’’ King said. “People are willing to invest in the industry again. It’s going to be tough for a few years to make those [races for young horses] go, but the future is looking really bright.’’